Gas turbine air compressor and control therefor

ABSTRACT

AN ARTIFICIAL SNOW PRODUCING SYSTEM EMPLOYING A NOVEL GAS TURBINE AIR COMPRESSOR WHICH HAS AN AIR BY-PASS CONNECTED TO DISCHARGE NOZZLES TO DELIVER COMPRESSED AIR TO THE LATTER FOR CO-MINGLING WITH WATER TO GENERATE SNOWLIKE WATER PARTICLES. THE GAS TURBINE COMPRESSOR IS PROVIDED WITH AN OVERLOAD PREVENTION SYSTEM TO AVOID EXCESS BY-PASS OF COMPRESSED AIR AND THE CONSEQUENT OVERHEATING AND FAILURE OF THE COMBUSTOR AND TURBINE COMPONENTS OF THE GAS TURBINE COMPRESSOR.

Sept. 2.1, 19.7.1 v E s, HRRlsON ETAL 3,606,971

v GAS TURBINE AIR COMPRESSOR AND CONTROL THEREFOR Filed may 28, 'i970 2 sheets-sheet 1 VSept. 21, 1971 Filed May 28, 1970 E. S. HARRISON ET AL l@As TURBINE AIR COMPRESSOR AND CONTROL. THEREFOR 70m/Ne I 2 sheets-sheet a United States Patent O 3,606,971 GAS TURBINE AIR COMPRESSOR AND CONTROL THEREFOR Emmett S. Harrison, Corona, N.Y., and August H. Zoll,

Cedar Grove, and Chapman J. Walker, Saddle River,

NJ., assignors to Curtiss-Wright Corporation Filed May 28, 1970, Ser. No. 41,509 Int. Cl. A01g 15/00; E01h 13/00 U.S. Cl. 239-14 14 Claims ABSTRACT OF THE DISCLOSURE An articial snow producing system employing a novel gas turbine air compressor which has an air by-pass connected to discharge nozzles to deliver compressed air to the latter for co-mingling with water to generate snowlike water particles. The gas turbine compressor is provided with an overload prevention system to avoid excess by-pass of compressed air and the consequent overheating and failure of the combustor and turbine components of the gas turbine compressor.

DISCLOSURE This invention relates to articial snow producing systems and, more particularly, to such systems employing novel turbojet engines to generate compressed air which may be utilized in conjunction with water to produce snow-like particles.

BACKGROUND Heretofore, in systems for the production of articial snow numerous conventional stationary or portable gas or electrically-driven compressors were used to provide the required compressed air, as is exemplied in U.S. Pats., No. 2,676,471; INo. 3,416,95l; and No. 3,494,559. These compressors are relatively costly and as many as 15 to 30 units, depending upon individual size and the size of the area to be covered with snow, may be necessary to produce the required amount of snow. In addition, these units create a relatively great amount of noise and pollution of the snow by droplets of lubrication oil and air pollution in the case of units driven by gasoline or diesel engines.

It is therefore, an object of this invention to provide a novel turbojet engine to generate compressed air for a snow-making system, which engine has suicient capacity to replace several conventional combustion engine driven reciprocable, rotary or axial-How type air compressors and, thereby, materially reduce, cost, noise and pollution of the air and snow.

It is another object of this invention to provide a novel turbojet engine for generating compressed air which engine cannot be overload and thus overheated and damaged by excessive demand for compressed air.

It is a further object of the present invention to provide in a snowmaking system an air compressor which requires no engine warm-up and, therefore, is capable of delivering full air capacity very quickly after start-up and 4at lower temperatures than conventional air compressor devices.

SUMMARY OF THE INVENTION Accordingly, the present invention contemplates a snowmaking system employing a novel turbojet engine (hereinafter referred to as a gas turbine air compressor) wherein a portion of the compressed air discharged from the compressor section is bled or by-passed, from its flow into the combustion section, to an outlet manifold. From the outlet manifold, the compressed air is passed, via an outlet pipe, to a cooler. The cooled compressed air is then passed ice to an accumulator manifold. A plurality of pipes connect with the manifold to conduct the compressed air to con'- ventional snowmaking nozzles which may be of the type disclosed in the U.S. Pats., No. 3,298,612; No. 3,301,485; No. 3,408,005; and No'. 3,494,559. Since the bled or bypassed air is at a pressure determined by the compressor ratio which corresponds to the amount of air bled or by-passed in relation to the total air ow passing through the compressor, quantities of by-passed compressed air in excess of a specified or predetermined maximum caused by excessive demand for compressed air at the point of use will result in insuillcient air ow through the combustion and turbine sections of the gas turbine compressor and overheating and failure of the components of those sections. To prevent this overheating and damage, the gas turbine compressor is provided with a safety control system according to this invention.

The safety control system comprises a flow control valve disposed in the air outlet pipe, which valve is connected to a means for actuating the valve to positions between fully open to fully closed. The valve is normally set in the fully open position so that under normal demand loads, where the compressor pressure ratio is high, compressed air will flow to the place of use. If the compressor ratio decreases below a preselected value upon an excessive demand load imposed on the gas turbine compressor, the valve will close an amount proportionate to the drop in pressure ratio to restore and maintain the preselected compressor pressure ratio. A pressure sensing 'and transmitting means is connected to the inlet and outlet portions of the compressor section to sense compressor inlet and outlet pressures. The pressure signals are transmitted to a controller which computes` the ratio of the pressures and compares the same relative to the preselected compressor pressure ratio value and, if the measured pressure ratio is below that of the preselected value, transmits an appropriate signal to the valve actuating means which effects movement of the valve toward a. closed position so as to restore the pressure ratio to the preselected value.

In one embodiment of this invention, the control system utilizes pressurized fluid, such as air, while another embodiment employs electrical components.

In both embodiments, the control system includes a signal means, visual and/or audible which Warns an operator that the compressed air demand rate exceeds the maximum predetermined amount the gas turbine air compressor can provide without overheating and damage. This signal means may comprise a switch which is actuated to close an electrical circuit to a warning means, such as a bell and/ or a light, when the valve is actuated from the fully open position.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more fully understood from the following detailed description thereof when considered in connection with the accompanying drawing wherein two embodiments of the invention are illustrated by way of examples, and in which:

FIG. 1 is a schematic illustration of a snowmaking system having a gas turbine `air compressor according to to this invention and safety control system therefor;

FIG. 2 is a schematic showing of another embodiment of the gas turbine air compressor; and

FIG. 3 is a graph showing the relationship between change in compressor pressure ratio and by-passed compressed air demand and turbine inlet temperature. i

DESCRIPTION OF THE PREFERRED EMBODIMENTS Now referring to the drawings and, more specically, FIG. 1, 10 generally designates a snow-producing system which essentially comprises a gas turbine air compressor 111 yaccording to this invention connected, through an outlet conduit means 12, to deliver compressed air to a discharge nozzle means 13 which may comprise a plurality of discharge nozzles of the type such as disclosed in the U.S. Pats., No. 3,298,612; No. 3,301,485; No. 3,408,005; and No. 3,494,559. In addition, system 110 has a water supply means 14, including pump 15, which is connected, via water conduit means 16, to deliver water to the discharge nozzle means 13, the latter providing for the atomization of the water with the compressed air and the discharge of the mixture into the atmosphere to thereby produce snow-like water particles.

The gas turbine air compressor 11 broadly comprises an elongated, generally cylindrical housing 17 having an air inlet opening 18 at one end thereof and an exhaust outlet opening 19 at the opposite end. A compressor assembly 20, which may be of the multistage, axial flow type, is disposed in housing 17 adjacent inlet opening 18 to draw air therethrough and compress such air. An annular outlet chamber 21 is formed adjacent compressor assembly 20 to receive compressed air from the latter. A gas turbine assembly 22, which may be of the multistage, axial flow type, is disposed in housing 17 adjacent exhaust outlet opening 19 and is connected, through a shaft 23, to drive the compressor assembly 20. A combustor 24 is disposed between compressor assembly 20 and turbine assembly 21 to communicate with annular outlet chamber 21 and receive compressed air from the latter. The combustor has fuel injection means and ignition means 26, such as spark plugs, to provide for light-olf and for burning of fuel and the generation of gaseous products of combustion. The combustor 24 is in communication with turbine assembly 22 so as to pass gaseous products of combustion to the turbine assembly and, thereby, effect rotation of turbine assembly 22. A bleed or by-pass manifold 27, toroidal in conguration, is provided adjacent outlet chamber 21 to provide for the bleeding or by-passing of compressed air discharging from compressor assembly 20 away from combustor 24 and turbine assembly 22. The gas tunbine compressor is constructed and arranged to provide for by-passing substantial quantities of compressed air, as for example, between 13,000 c.f.m. (cubic feet per minute) and 50 p.s.i.g. (pounds per square inch gage) and 26,650 c.f.m. at 85 p.s.i.g., depending upon size. The value lof the by-passed compressed air outlet pressure, relative to the air pressure at the inlet of the compressor, hereinafter referred to as compressor pressure ratio, corresponds to the amount of air bled or by-passed in relation to the total air flow from compressor assembly 20 into inlet chamber 21. Thus, when quantities of compressed air in excess of a predetermined maximum, as measured by a decrease in cornpressor pressure ratio below a selected compressor pressure ratio, insucient volume of air will ow through combustor 24 and turbine assembly 22 and result in overheating and damage to the components of those assemblies. The relationship of compressor pressure ratio, turbine inlet temperatures and the amount of airbleed or by-passed compressed air, is illustrated by the graph shown in FIG. 3. As clearly shown in the graph, the compressor pressure ratio varies inversely as the amount of airbleed varies, while turbine inlet temperature varies directly as the amount of airbleed varies. Thus, it is evident that compressor pressure ratio is a measure of the amount of airbleed and that a compressor pressure ratio may be selected to represent the maximum amount of airbleed acceptable Without danger of damage to the combustor or turbine due to overheating. As shown in FIG. 3, the predetermined or reference compressor pressure ratio may be established at the intersection of the line labelled normal and the line, P3/P2, representing the compressor pressure ratio curve. To prevent this overheating and damage to the gas turbine air compressor due to excessive compressed air demand or load thereon,

4 gas turbine air compressor 11 is provided with a safety control system 28, according to this invention.

The safety control system 28, as shown in FIG. 1, comprises electronic components and a control valve 29 disposed in an outlet pipe 30 which forms part of conduit means 12. The pipe 30 is connected at one end to manifold 27 to conduct compressed air from the latter. The control valve 29 is normally in a fully open position which it retains until the amount of compressed air demand exceeds the predetermined maximum amount. The electronic components include suitable pressure-to-current transmitters 31 and 32 which may be of the type manufactured by Fischer and Porter Company of Warminster, Pa., U.S.A., and designated type Series 50 EP 1000. The transmitter 31 is in communication with inlet opening 18 of gas turbine air compressor 11, via a line or pipe 33, to conduct or, in effect, sense inlet air pressure, P2, while transmitter 32 is in communication with manifold 27, via a line or pipe 34, to conduct or, in effect, sense the pressure, P3, of compressed air being by-passed into outlet pipe 30. Each of the transmitters 31 and 32 functions to measure the fluid pressure conducted thereto and convert the same into a voltage signal which is transmitted to a controller 35. The voltage signals, from transmitters 31 and 32, are transmitted to controller 35 by way of electrical conduits 36 and 37, respectively. The controller 35 may be of any suitable type, such as the electronic controller of the kind manufactured by Fischer and Porter Company, Warminster, Pa., U.S.A., and designated Series 53 EL 3000 and identified by the trademark Scan-line." The controller 35 is capable of adjustment to produce specied voltage equivalent to a predetermined pressure ratio to establish a reference value. The controller 35 is also constructed and arranged to compute electronically the compressor pressure ratio, as indicated by the voltage signals conducted to the controller, via lines 36 and 37, and electronically compare this compressor pressure ratio with the predetermined or reference pressure ratio. If the measured compressor pressure ratio is at or higher than the predetermined or reference pressure ratio, no output signal is generated by the controller and valve 29 remains in the fully open position. If the measured pressure ratio falls below the predetermined or reference pressure ratio, the controller emits an electric output signal proportional to the difference in pressure ratios which is conducted to a valve actuator 38 by an electrical conduit 39. The valve actuator may be of conventional construction and may have a sere-motor connected to one end of a linkage assembly 40 which interconnects the servo-motor with the valve 29 to effect actuation of the latter.

In operation of safety control system 28, transmitters 31 and 32 constantly monitor the compressor air inlet pressure, P2, and compressed air pressure, P3, in manifold 27 through pressure lines 33 and 34, respectively. Each of the transmitters 31 and 32 generate electrical voltage signals proportionate to the sensed pressures, P2 and P3, which are conducted, via electric conduits 36 and 37, to controller 35. The controller 35 electrically divides the input voltage signals to produce a voltage signal representative of the ratio between P2 and P3. This ratio voltage is compared with the predetermined or reference ratio voltage by controller 35. If the measured ratio voltage is lower than the reference voltage, controller 35 transmits, via electrical conduit 39, an output signal which effects operation of valve actuator 38 and, through linkage assembly 40, movement of valve 29 toward a closed position. The valve 29 modulates until the ratio between P2 and P2 is restored to or ireaches a value above the predetermined or reference pressure ratio. When at least minimum pressure ratio is restored, valve actuator 38 etfects movement of valve 29 back to the fully open position. lf the excessive demand condition continues to exist, contoller 35, upon determining that the pressure ratio between P2 and P3 is again below the reference pressure ratio, will cause valve actuator 38 to again move valve 27 towards the closed position and establish the minimum allowable pressure ratio. Since the reference pressure ratio is selected to be equivalent to a safe maximum compressed air demand or load which gas turbine air compressor 11 can deliver without overheating and damage to the combustor and turbine components, the gas turbine air compressor is automatically protected from this inadvertent damage and still provides maximum permissible airflow at all times.

To alert :an operator of the snowmaking system to the existence of an overload or excessive compressed air demand on gas turbine air compressor 11, an 4alarm circuit 41 may be provided. As shown, the alarm circuit 41 may comprise a micro-switch 42, mounted on outlet pipe 30 adjacent valve 29, which switch is electrically connected to a source of electrical current and a warning means 43, such as an alarm bell and/or warning light. The micro-switch 42 has an actuating plunger 44 which is positioned relative to valve 29 so that upon movement of valve 29, from the normally open position, toward a closed position, as shown by the dot-dash line, the plunger 44 is moved to close the switch and thereby complete the electrical circuit to the warning means 43, and, in turn, visually and/or audibly alert an operator to this undesirable overload condition, while the valve modulates to hold the minimum pressure ratio.

The snowmaking system 10, in addition to the above described gas turbine air compressor 11, comprises a cooler 45 connected to pipe 30 to receive compressed air. The cooler 45 may be of any suitable construction, well known to those skilled in the heat exchange art, Which is capable of passing the relatively hot compressed air into indirect heat exchanger relationship with a cooling fluid, such as atmospheric air. From cooler 45, the cooled compressed air is conducted by pipe 46 to accumulatormanifold 47. From accumulator-manifold 47, the cornpressed air is delivered to the plurality of nozzles 13 by Way of a plurality of branch pipes 48. f, as shown in FIG. l, the system 10 comprises one or more additional gas turbine air compressors 11, such as other gas turbine air compressor 11A are connected to a cooler 45A, similar to cooler 45 and accumulator-manifold 47, check valves -49 are disposed in pipes 46 and 46A respectively. The check valves 49 are of particular importance in an installation wherein one of the gas turbine air compressors is shut down for repair or inspection or is on stand-by status while the other is in operation, to prevent loss of compressed air and protect the idle gas turbine air compressor from damage.

As previously described system 10 includes a water pump 15 which pumps water, from a source thereof, through conduit means 16, to discharge nozzles means 13. The conduit means 16 comprises a pump outlet pipe 50, a water manifold 51 which is connected to outlet pipe 50 to receive water therefrom and a plurality of branch conduits l52 for conducting the water to each of the plurality of discharge nozzles means 13.

In FIG. 2 is shown an alternative safety control system, designated 28A, for a gas turbine air compressor. Essentially, the safety control system 28A shown in FIG. 2 differs from safety control system 28 illustrated in FIG. 1 in that it is a pneumatic system as distinguished from the electronic system of FIG. 1. The safety control system 28 is useable in conjunction with a gas turbine air compressor 11A similar to gas turbine air compressor 11 shown in FIG. 1. Since gas turbine air compressor 11A shown in FIG. 2 is similar to gas turbine air compressor 11, parts of gas turbine air compressor 11A corresponding to like parts of gas turbine air compressor 11 will be designated by the same number but having the suffix A added thereto.

As shown in FIG. 2, the pneumatic safety control system 28A comprises two pneumatic pressure transmitters 54 and 55 which are in communication, through pressure lines or pipes 56 and l57, respectively, with inlet opening 18A and outlet chamber 21. The pipes 56 and 57 function to transmit air pressure, P2 and P3, at inlet opening 18A and outlet chamber 21A, respectively, to transmitters 54 and `55. A source of pneumatic pressure, such as air cornpressor 58, is connected, via pipe 59, to pressure transmitters =54 and 55. This separate source of pneumatic pressure provides the safety control system with a control pressure so that an output pressure is generated in the transmitters which is proportional to the input pressures P2 yand P3. This output pneumatic pressure generated by pressure transmitters 54 and 55 is conducted by pipes 60 and 61, respectively, to a pneumatic controller 62. The pressure transmitters l54 and 55 may be of any suitable type, such as the pneumatic pressure transmitters of the type, KD 14, manufactured by Bailey Meter Company, Wickliffe, Ohio. The pneumatic controller 62 is constructed and arranged to divide the pressure signal corresponding to P2 into the pressure signal corresponding to P3, which resultant pressure ratio is compared with a reference or predetermined pressure representing the least pressure ratio at which gas turbine air compressor 11A can operate without overheating and damage to the components of combustor 24A and turbine 22A. If the controller senses a decrease in the measured pressure ratio as compared with the reference pressure ratio, the controller effects the actuation of control valve 29A toward a closed position through a conventional diaphragm type servo-mechanism `63 and linkage assembly 64. The control valve 29A modulates in the closed direction to bring the pressure ratio back to the predetermined value in the same manner as previously described with respect to the embodiment shown in FIG. 1. The controller 62 is connected to a control pressure via pipe 65. The controller is of any suitable construction and may be of the type manufactured by Bailey Meter Cornpany of Wickliie, Ohio and designated 500 Hand/Automatic Station with Adjustable Set Point and commercially sold under the trademark Mini-line. The control system 28A herein above described may also include a warning means (not shown) of the type shown and described in connection with safety control system 28.

It is now believed readily apparent that the present invention provides a novel artificial snowmaking system having a novel gas turbine air compressor which system is capable of producing very large quantities of articial snow relatively noiselessly and with no ground or air pollution. In another aspect of the invention, a safety control system is provided which protects the gas turbine air compressor against overheating and damage due to an excessive demand thereon for compressed air at the point of use.

Although various embodiments of the invention have been illustrated and described in detail, it is to be expressly understood that the invention is not limited thereto. Various changes can be made in the arrangement of parts without departing from the spirit and scope of the invention, as the same will now be understood by those skilled in the art. For example, in place of pipes 33 and 34 of the safety control system 28 (see FIG. l), piezo-crystals may be employed to sense air pressures, P2 and P3 and transmit voltage signals to controller 62.

What is claimed is:

1 In an artificial snow producing system comprising discharge nozzles for co-mingling compressed air and Water and discharging the same into the atmosphere, the combination of a. gas turbine air compressor having a combustor, a gas turbine and an air compressor driven by the gas turbine which is driven by products of cornbustion generated by compressed air and fuel burned in the combustor and having a by-pass means communicating with the compressor to by-pass some of the compressed air owing to the combustor, means for cooling the bypassed compressed air, a supply of water, and outlet conduit means communicating with said by-pass means for receiving from the latter by-pass compressed air and conducting the compressed air to the discharge nozzles for co-mingling with the -water and the generation of snowlike water particles.

2. The apparatus according to claim 1 wherein said cooling means is disposed in the outlet conduit means.

3. The combination of claim 1 wherein a compressed air distribution manifold is provided and to which said discharge nozzles are connected to receive compressed air and wherein a plurality of gas turbine air compressors are connected to deliver, through their respective outlet conduit means, compressed air to the air distribution manifold.

4. The combination of claim 3` wherein each of said plurality of gas turbine air compressors are provided with a safety control system which automatically effects a safe modulation of compressed air flow into and through the by-pass means in response to compressed air demand in excess of a predetermined amount to thereby prevent overheating and damage to the combustor and turbine.

5. The combination of claim 1 wherein each of the outlet conduit means is provided with a check valve to prevent ow of compressed air from one gas turbine air compressor through the air distribution manifold into another gas turbine air compressor.

6. The combination of claim 1 wherein a safety control system is provided which automatically eifects modulation of compressed air llow into and through lthe bypass means in response to compressed air demand in excess of a predetermined amount to thereby prevent overheating arrd damage to the combustor or turbine.

f7. The combination of claim 6 wherein said safety control system includes -a warning device which is operative in response to a compressed air demand in excess of said predetermined value.

8. The combination of claim 1 wherein a safety control system is provided fwhich comprises:

I(a) valve means disposed in a normally open position in said outlet conduit means;

(b) transmitter means for sensing compressor inlet and outlet air pressure and transmitting signals corresponding to such air pressures;

(c) controller means connected to said valve means and to the transmitting means lto receive the signals from the transmitter means `and when the pressure ratio decreases from a predetermined pressure ratio respond thereto and cause the valve means to move to a closed position and modulates compressed air flow through the outlet conduit means until the predetermined pressure ratio is restored.

9. A combination of cl-aim 7 whereinsaid safety control system includes a warning device which is energized when the valve means moves toward a closed position to alert an operator that the pressure ratio has decreased below the predetermined value.

10. The combination of claim 1 wherein an electrical safety control system is provided which comprises:

(a) valve means disposed in a normally open position in said outlet conduit means;

(b) a transmitter means for sensing compressor inlet and outlet air pressure and transmitting electrical signals corresponding to such air pressures; and

(c) controller means connected to said valve means and to the .transmitter means to receive the electrical signals from the transmitter means and respond to actuate said valve means toward a closed position when the signals indicate a decrease in pressure ratio from a predetermined pressure ratio.

11. The combination of claim. 1 wherein a pneumatic safety control system is provided which automatically effects a modulation of compressed air flow into and through the by-pass means in response to compressed air demand in excess of a predetermined amount to thereby prevent overheating and damage to the combustor or turbine.

12. In an artificial snow producing system having discharge nozzles for co-mingling compressed air and water and discharging the same. into the atmosphere, the combination of a gas turbine air compressor, having a combustol gas turbine and an air compressor driven by the gas turbine which is driven by products of combustion generated by compressed air, bleed means communicating with the compressor to by-pass some of the compressed air away from the combustor, means for cooling the by-passed compressed air, a supply of Water, an outlet conduit means communicating with the bleed means for receiving from the latter by-passed compressed air and conducting the same to the discharge nozzles for comingling with the water and the generation of snow-like water particles, and a safety control system comprising a valve means in said outlet conduit means disposed in' a normally open position and sensing, signal transmitting and actuating means connected -fto said valve means to automatically effect actuation of the valve means toward a closed position in response to compressed lair demand in excess of a predetermined amount to thereby prevent overheating and damage to the combustor or turbine.

13. The combination of claim 12 wherein said sensing, signal transmitting and actuating means comprises:

(a) transmit-ting means;

(b) sensing elements disposed to sen-se compressor inlet and outlet air pressure and connected to the transmitting means;

(c) said transmitting means generating and transmitting signals corresponding to such air pressures; and

(d) controller means connected to said valve means a-nd to the transmitting means to receive the signals from the laltter and convert the same into a pressure ratio so that when the pressure ratio decreases from a predetermined pressure ratio the controller means elects actuation of the valve means toward a closed position to modulate compressed air flow bleed until .the predetermined pressure ratio is restored.

14. The combination of claim 12 wherein said cooling means is disposed in the outlet cond-uit means to receive and cool compressed air owing through the outlet conduit means and pass the cooled compressed air to the discharge nozzles.

References Cited UNITED STATES PATENTS 3,126,155 3/1964 Lohse 239-414 3,429,507 2/1969 Jones 239-14X 3,438,576 4/1969 Handman 239-2 3,517,512 6/1970 Anderson et al. Z39-2X LLOYD L. KING, Primary Examiner U.S. Cl. X.R. 239-28 

